Electrolytic process of making alkali perborates.



oNITED sTArus FATENT OFFICE;

OTTO LIELKNECHT, OF FBANKFORT-ON-THE-MAIN, GEBMANY ASSIGNOR TO THE ROESSLER 8c HASSLACHER CHEMICAL 00., OF NEW YORK, 11'. Y., A CORPORATION OF NEW YORK.

ELECTROLYTIC PROCESS OF MAKING ALKALI PEBBOBATES.

No Drawing.

To all whom it may concern:

Be it knownthat I, ()r'ro Ln-mKNEonT, a subject of the Emperor of Germany, residing at Frankfort-omthe-Main, Germany, have invented certain new and useful Improvements in Electrolytic Processes of Making Alkali l-erborates,of which the following is a specification.

This process relates to the art of making perborates and it particularly relates to a process for the electrolytic production of sodium perborate by an electrolytic process.

it is known that alkali perborates may be obtained bydouble decomposition of alkali percarbonate's withalkali borates; it is also known that alkali percarbonates may be H so , roduced by the electrolysis of alkalicar- It has therefore been a problem of technical importance to investigate whether or not it would be possible to produce percarbonates electrolytically in an economical way and to simultaneously cause them to react with borates, thereby producing perborates. The success of such an enterprise would seem to be discouraged by the many difiiculties met in the effort to substantiate the proposition. If for instance an alkali carbonate solution is elertrolyzed, the yield, though satisfactory at the beginning, falls in relatively short time to zero. The same phenomenon occu1's when electrolyzlng an alkali carboiia-te solution containing also borax; furthermore in this electrolytic process there is a point where just as much active oxygen s generated in the form of per-carbonate as is reduced at the cathode, i. a. there is an equilibrium in the process.

Therefore it appeared to be rather hopeless to attempt to obtain perborates by such t )rocess as a double decompositionbetween l in electrolytically generated percarbonate and the borates. I have discovered, however,

and Irade the surprising observation that it is possible to produce, for instance sodium perborate, in an economical. way if the 'electrolysis is carried, out in the presence of ,solid sodium perborate, i. e, ifsodium perhorate is present ;in the solid immaterial for the success of t e process in ters the solution. The sodium perborate may Specification of Letters intent.

phase. It is Patented Aug. '7, 1917.

Application filed January 6, 1918. Serial No. 70,592.

be enerated spontaneousy during the electro ysis of a solution containing soda and borax, or it ma be generated by cooling the temperature 0 the electrolyte relativel. a short time after electrolysis has starte so that at least part of the enerated erborate is thereby precipitated, ut I fin it more suitable to add solid perborate soon after the electrolysis has started or to add immediately from the beginning so much erborate to the solution that sodium per orate is present in solid form, 1'. e. in the solid phase.

disadvantage may be counteracted'by adding,

to the solution either continuously or at suitable intervals, preferably while stirring the same, as much borax as is transformed-in the form of 'perborate, thus continuously replenishing the borax whereby a highly satura'ted solution of borax is obtained. ByI i carrying out the process in this way I sue ceed in transforming great quantities of borax into sodium perborate," by one operation.

I find it advantageous in this process to appl the raw material practically free fromcata yzers, though I may render harmless any catalyzer w the solution, by adding for instance a negative catalyzer, as for instance stannic acid or magnesium-silicate.

It is especially advantageous to add one or several substances serving as accelerating agents and exerting a favorable influence on the reaction to the electrolyte, as for instance alkali bicarbonates or materials generating the same. The substances mentioned above also seem to exert their influence in the same direction.

When I am using both in the specification and the claims the expressions,- solid alkali perborate, an excess of an alkali perborate,

ich might happen to be in sodium perborate.

urified in the presence ofisolid sodium perorate.

23. The process of making sodium perborates, consisting in preparing a solution of sodium carbonate and borax previously freed from catalytic agents and electrolyzing said solution in the presence of solid 2a. The process of making sodium perborates, consisting in electrolyzing a solution of sodium carbonate and borax 1n the presence of solid sodium perborate and adding to the solution a substance serving as an accelerating agent.

25. The process of making sodium perborates consisting in electrolyzing a solution of sodium carbonate and borax in the presing witnesses.

of sodium carbonate and borax free from catalytic agents, in the presence of solid sodium perborate and adding sodium bicar bonate as an accelerating agent.

' In testimony whereof I have signed this specification in the presence of two subscriborro LIEBKNECHT.

Witnesses J EAN GRUND, CARL GRUND. 

